The parents of Otto Warmbier have filed a claim for a seized North Korean cargo ship, seeking to collect on a multimillion-dollar judgment awarded in the American college student’s death.

The Warmbiers filed court papers Manhattan federal court saying they have a right to the assets after North Korea failed to respond to a wrongful death claim that accused it of abducting Warmbier, who had traveled there for a guided tour ahead of a study abroad program in Hong Kong.

“The Warmbiers are committed to holding North Korea accountable for the death of their son Otto, and will work tirelessly to seize North Korean assets wherever they may be found,” Ben Hatch, an attorney for the family, said in an emailed statement.

North Korea has rejected accusations by relatives that it tortured Warmbier and said he was provided “medical treatments and care with all sincerity.”

President Donald Trump has condemned Warmbier’s treatment but said earlier this year he did not believe North Korea’s leader, Kim Jong Un, knew about it or would have allowed it to happen.

North Korea did not respond to the wrongful death lawsuit that accused it of detaining Warmbier at the Pyongyang airport “in an attempt to extract various concessions from the United States government.”

US District Judge Beryl Howell ruled last year that North Korea “more likely than not barbarically tortured Otto to extract a false confession” and used his lengthy prison sentence as leverage to further its foreign policy objectives.

She ordered North Korea to pay $501 million for its “barbaric mistreatment” of Warmbier, saying the student’s family “experienced North Korea’s brutality first-hand.”

In the latest court filings, Warmbier’s parents claim a right to the North Korean cargo ship, the “Wise Honest,” which the US seized in May because it was carrying coal in violation of U.N. sanctions.

The vessel, North Korea’s second-largest cargo ship, was first detained in April 2018 by Indonesia while transporting a large amount of coal. The US later announced it had seized the 17,061-ton carrier in a first-of-its kind enforcement that came amid a tense moment in relations with North Korea.